1. Field of the invention
This invention relates to a disc brake, and more particularly to a disc brake device for a vehicle, with the freedom of a dragging phenomenon which has ever arisen with a prior art device upon releasing the brakes.
2. Description of the prior art
A disc brake is known, which has caliper slidable in parallel to the axis of rotation of a brake disc. This type disc brake has been such that a pair of pad assemblies are supported on the opposite sides of the brake disc slidably along the axis parallel to the axis of rotation of the brake disc. The pair of pad assemblies are urged toward the brake disc into frictional engagement with the opposite side surfaces of the brake disc by operation of a piston incorporated in the caliper and reaction thereof, thereby applying a braking action to the brake disc. When the piston is released from the operative state, the frictional engagement of the pair of pad assemblies with the brake disc is released by the resilient returning force of retraction seal members disposed between the caliper and the piston.
In the prior art disc brake, the pressure bearing opposite surfaces of the brake disc make a right angle with respect to the axis of rotation of the brake disc, and the pair of pad assemblies are movable only along a path parallel to the axis of rotation of the disc. Furthermore, movement in a direction to release the braking action, of the pair of pad assemblies has been dependent on the resilient returning force alone of the retraction seal members. However, the retraction stroke of the seal members could not be large enough to return the pair of pad assemblies from the engaging position with the pressure-bearing opposite side surfaces of the brake disc to their home positions. For this reason, dragging phenomenon has very often arisen with the prior art disc brake. The dragging phenomenon causes an increased consumption of fuel of the vehicle, and leads to a squelch groan which is an unusual sound of the brakes.